1. Field of the Invention
The present invention relates to a hub clutch assembly for a vehicle, for engaging and disengaging a drive axle to and from a wheel.
2. Description of the Prior Art
A "DEVICE FOR DISCONNECTING WHEEL FROM OPTIONAL DRIVE FOR AXLE" is disclosed in Japanese Patent Application Laid-Open No. 60-151103. The device is arranged such that, in a four-wheel drive (4WD) vehicle, a pair of front wheels or a rear wheels on the disconnected side are disconnected from their respective drive axles at two-wheel drive running, to prevent vibration or noises, and to improve specific fuel consumption and durability. The device comprises a clutch for connecting and disconnecting one of the drive axles to and from a corresponding wheel and an actuator for operating the clutch.
In the above-described device, the actuator is formed by utilization of a housing on the side of the wheel as a cylinder.
The housing is constructed as a hermetic or closed structure in order to protect an interior mechanism within the housing from foreign matters such as dust or dirt, muddy water or the like, and a closed chamber is defined between the actuator and a top of the housing.
There are situations in which the temperature inside the closed chamber is brought to a hundred and several-ten degrees (.degree.C.) due to heat from the brakes, and internal pressure is raised to approximately 1.35 atm. Further, there is a fear that, if pressure leaking from the side of the actuator accumulates, the internal pressure will be further raised. Also, there is a fear that malfunction of the clutch may occur due to internal pressure within the closed chamber, or that operation of the actuator will be prevented in such a way that the clutch cannot operate normally. In order to prevent these situations from arising, an opening on which a filter is mounted has been provided in the closed chamber.
However, it is impossible for the filter to perfectly prevent the foreign matters from invading, and there is a fear that, if invading muddy water becomes frozen and solidified, the clutch will become inoperable.